Refrigerator with regulable dehumidification

ABSTRACT

A no-frost refrigerator includes at least one storage compartment, an evaporator, which can be switched on and off and is disposed in a chamber that is separate from the storage compartment, and a fan for driving an exchange of air between the storage compartment and the chamber. Of the evaporator and fan, at least one can be operated while the other is switched off.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of copending InternationalApplication No. PCT/EP02/13806, filed Dec. 5, 2002, which designated theUnited States and was not published in English.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a no-frost refrigerator. In the case ofsuch refrigerators, an evaporator is disposed, for example, in a chamberthat is separated from a storage compartment for articles that are to becooled, and an exchange of air between the chamber and the storagecompartment, by which the latter is cooled, takes place in that, withthe aid of a fan on the evaporator, cooled and dried air is blown intothe storage compartment and relatively warm, humid air is taken out ofthe storage compartment into the chamber. In such a case, the storagecompartment is not just cooled, but also dehumidified. The moisturecondenses on the evaporator. This dehumidification preventsrefrigeration where, under critical climatic conditions, particularly ifthe refrigerator is used in warm surroundings with a high level of airhumidity, condensation condenses on set-down surfaces and articles thatare to be cooled in the storage compartment. However, in the case ofless critical ambient conditions, this advantage may turn into adisadvantage if stored foodstuffs are dried out by the intensivedehumidification.

Also known are so-called hybrid refrigerators in which the evaporator isin direct thermal contact with the storage compartment and a fan is usedto produce an air flow in the storage compartment that passes over anevaporator-cooled side wall of the storage compartment and, thus,intensifies the exchange of heat between the storage compartment andevaporator. In the case of these hybrid appliances, the dehumidifyingaction is less intensive than in the case of a no-frost appliancebecause moisture that has condensed on the cooled wall of the storagecompartment, over non-operational periods of the evaporator, has theopportunity of evaporating back into the storage compartment. This alsomeans, however, that, under critical use conditions, the risk of theundesired formation of condensation is higher in the case of suchappliances than in the case of a no-frost appliance.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a refrigeratorwith regulable dehumidification that overcomes the hereinafore-mentioneddisadvantages of the heretofore-known devices of this general type andthat is capable, under diverse climatic conditions, of achieving afavorable compromise between the risk of the formation of condensationin the storage compartment and the risk of drying out the articles thatare to be cooled.

With the foregoing and other objects in view, there is provided, inaccordance with the invention, a no-frost refrigerator, including atleast one storage compartment, heat insulation, an evaporator disposedseparate from the at least one storage compartment with the heatinsulation, and a fan for driving an exchange of air between the storagecompartment and the evaporator, at least one of the evaporator and thefan being operated while the other one of the evaporator and the fan isswitched off.

Operating the fan when the evaporator has been switched off assists themoisture condensed on the evaporator from being evaporated back into thestorage compartment, and, thus, combats the drying out of articles thatare to be cooled.

For moisture to be evaporated back, it is most effective if the fan isoperated toward the end of a switched-off phase of the evaporator, whenthe latter is in the defrosting phase, at a point in time where theevaporator is relatively warm and moisture condensed thereon evaporatesmore readily than at the beginning of a switched-off phase, where themoisture is, generally, completely frozen on the evaporator.

With respect to the efficiency of the refrigerator, it is desirable forthe fan also to be operated at the beginning of a switched-off phase ofthe evaporator, to, thus, utilize a temperature gradient that stillexists at the time between the storage compartment and the evaporatorfor cooling the storage compartment.

A particularly straightforward solution here is to operate the fancontinuously when the evaporator has been switched off.

In accordance with another feature of the invention, there is provided acontrol circuit connected to the evaporator and the fan for controllingoperation of the evaporator and the fan, the circuit operating the fancontinuously when the evaporator has been switched off.

In accordance with a further feature of the invention, the evaporator isoperated when the fan has been switched off.

In accordance with an added feature of the invention, the controlcircuit regulates operation of the evaporator when the fan has beenswitched off to keep a temperature of the evaporator at least one ofbelow a temperature of the storage compartment and below 0° C.

In accordance with an additional feature of the invention, the controlcircuit regulates operation of the evaporator when the fan has beenswitched off to keep a temperature of the evaporator at least one ofbelow a temperature of the storage compartment and below 0° C.

Furthermore, it is desirable to also operate the evaporator when the fanhas been switched off. It is, thus, possible, between two “normal”cooling phases of the refrigerator, in which the evaporator and fan areoperated together, for the temperature of the evaporator always to bekept below the temperature of the storage compartment, preferably, below0° C., to, thus, limit the evaporation from the evaporator back into thestorage compartment to an unavoidable minimum.

In the case of a straightforward configuration of the invention, therefrigerator has an operating-mode selector switch by which a controlcircuit that controls the operation of the evaporator and of the fan canbe switched over between at least two of the following operating states:

-   -   a) operation of the evaporator when the fan has been switched on        and, at least temporarily, when it has been switched off;    -   b) simultaneous operation of the evaporator and of the fan; and    -   c) operation of the fan when the evaporator has been switched on        and, at least temporarily, when it has been switched off.

This makes it possible for the user, by changing over the operation-modeselector switch from operating state a) to b) or from b) to c), tocombat the undesired formation of condensation in the storagecompartment or, by changing over from operating state c) to b) or fromb) to a), to limit undesired drying out of the articles that are to becooled.

Alternatively, or as a supplement, the refrigerator may also be equippedwith a humidity sensor, the control circuit automatically switching overbetween at least two of the operating states a), b), and c) independence on a measured value of the humidity sensor.

Such a humidity sensor is, preferably, disposed on the storagecompartment; however, it is also conceivable for the sensor to be fittedoutside the storage compartment so that the humidity sensor can sensethe humidity of the ambient air (and, thus, the amount of moistureintroduced into the storage compartment each time the door is opened).

In accordance with yet another feature of the invention, in theoperating state a), the control circuit, in each switched-off phase ofthe fan, keeps the evaporator temporarily switched off and temporarilyswitched on.

In accordance with yet a further feature of the invention, in theoperating state a), the control circuit, in each switched-off phase ofthe fan, periodically switches the evaporator on and off.

In accordance with yet an added feature of the invention, in theoperating state c), the control circuit operates the fan continuously ineach switched-off phase of the evaporator.

In accordance with yet an additional feature of the invention, theevaporator is disposed in the storage compartment and is encapsulated bythe heat insulation.

In accordance with again another feature of the invention, there isprovided an evaporator compartment disposed separately from the storagecompartment with the heat insulation, the evaporator being disposed inthe evaporator compartment.

With the objects of the invention in view, there is also provided ano-frost refrigerator, including at least one storage compartmentdefining an interior, heat insulation, an evaporator disposed in an areaseparate from the interior of the at least one storage compartment withthe heat insulation, and a fan for driving an exchange of air betweenthe interior of the storage compartment and the area of the evaporator,at least one of the evaporator and the fan being operated while theother one of the evaporator and the fan is switched off.

Other features that are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a refrigerator with regulable dehumidification, it is, nevertheless,not intended to be limited to the details shown because variousmodifications and structural changes may be made therein withoutdeparting from the spirit of the invention and within the scope andrange of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block circuit diagram of a no-frost refrigerator accordingto the invention;

FIG. 2 is a timing diagram for the operation of the evaporator and fanof FIG. 1 in accordance with a first operating state of the invention;

FIG. 3 is a timing diagram for the operation of the evaporator and fanof FIG. 1 in accordance with a second operating state of the invention;and

FIG. 4 is a timing diagram for the operation of the evaporator and fanof FIG. 1 in accordance with a third operating state of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawings in detail and first,particularly to FIG. 1 thereof, there is shown a refrigerator that isconfigured with combined refrigerating and freezing functions and inwhich the present invention is realized. A cooling compartment 1 and afreezing compartment 2 form two temperature zones of the refrigerator. Arefrigerant circuit includes a compressor 3, which pumps a compressedrefrigerant successively through two evaporators 4, 5 of the freezingcompartment 2 and of the cooling compartment 1, respectively, and a heatexchanger 6, through which the refrigerant, which is expanded in theevaporators 4, 5, runs before entering into the compressor 3, again. Inthe present case, the evaporator 5, which is associated with the coolingcompartment 1 and is configured as a lamellar evaporator, isaccommodated in a chamber 8, which is separated off from the coolingcompartment 1 by a thermally insulating wall 7. The chamber 8communicates with the cooling compartment 1 through air-inlet andair-outlet openings, a fan 9 that is intended for driving the exchangeof air between the chamber 8 and the cooling compartment 1 beingdisposed in one of these openings.

A control circuit 10 is connected to a temperature sensor 12, which isdisposed in the cooling compartment, and to the compressor 3 and the fan9 through control lines and is capable of switching the compressor 3 andthe fan 9—and, directly through the compressor 3, the evaporators 4,5—on and off in dependence on a temperature sensed by the temperaturesensor 12. The control circuit 10 has three operating states a), b), andc), and a user can select one of these operating states by actuating aselector switch 11.

The normal operating state b) corresponds to the conventional operationof a no-frost refrigerator; a timing diagram for this operating state isshown in FIG. 3. If the temperature measured by the temperature sensor12 in the cooling compartment 1 exceeds a first limit value, the controlcircuit 10 switches on the evaporator 4 and the fan 9 substantiallysimultaneously, this being illustrated in each case by high levels ofthe curves 4 b and 9 b respectively illustrating the operating states ofthe evaporator 4 and the fan 9. If, once a period of a few minutes haselapsed, the temperature in the cooling compartment 1 drops below asecond limit value that is lower than the first, then the controlcircuit 10 switches the evaporator 4 and fan 9 off again, this beingillustrated as low levels of the curves 4 b, 9 b. During the operatingperiods of the fan 9, the evaporator 4, with the possible exception of ashort period as it begins to operate, is cooled, and moisture that iscarried out by air coming from the cooling compartment 1 condenses onthe evaporator 4. In the switched-off phases of the evaporator 4, themoisture frozen on the evaporator can thaw and flow away and is removedfrom the refrigerator.

If a user establishes that an undesirably large amount of moisture is,nevertheless, condensing in the cooling compartment 1, then he/she canswitch over the selector switch 1 to the operating state a), of whichthe timing diagram is illustrated in FIG. 2 by operating-state curves 4a and 9 a of the respective evaporator 5 and fan 9. In operating statea), the phases 19 of simultaneous operation of the evaporator and fanare substantially no different from those of the operating state b);their start and end are each defined with reference to the measuringresult of the temperature sensor 12. However, while the fan remainsswitched off between two such simultaneous operating phases 19 of theevaporator and fan, the switched-off or non-operational phase 20 of theevaporator 5 is interrupted in each case by short operating phases 21.The duration of the short operating phases 21 is such that theevaporator 5 is reliably kept at a lower temperature than the coolingcompartment 1, preferably, below 0° C., and, thus, moisture frozen onthe evaporator 4 is prevented from evaporating back into the coolingcompartment 1.

The position in time and the duration of the short operating phases 21may be regulated, in a manner analogous to the operating phases 19, by atemperature sensor that is connected to the control circuit 10, but,nevertheless, is disposed on the evaporator 5; alternatively, however,it is also possible for the control circuit 10 to produce the shortoperating phases 21 in a fixedly predetermined time pattern. In such acase, the time interval between the end of one operating phase 19 andthe first short operating phase 21 that follows is greater than theinterval between the short operating phases 21, because it is assumedthat, at the end of each operating phase 19, the evaporator 5 is at atemperature that is considerably lower than freezing and, in the firstinstance, requires some amount of time to heat up to the extent where ashort operating phase 21 is necessary, the temperature of the chamber 8that is to be maintained by the short operating phases 21 being closerto 0° C. than the temperature that is reached at the end of theoperating phase 19.

If the low temperature of the evaporator 5 is maintained over a largenumber of cycles each including the operating phase 19 and switched-offphase 20, an increasingly thick layer of ice forms over time on theevaporator 5, this layer of ice being detrimental to the effectivenessof the evaporator. To prevent such formation of ice, the evaporator maybe equipped with an electric heating device that makes it possible,within a single switched-off phase 20 that is not interrupted byoperating phases 21, to thaw the layer of ice and allow it to flow away.Instead of such a heating device, however, it is also possible forprovision to be made for the control device 10, in the operating statea), from time to time, not to introduce switched-off phases that areinterrupted by the short operating phases 21 and give the evaporator 5the opportunity of defrosting.

If, in contrast, a user of the refrigerator establishes that articlesthat are to be cooled in the cooling compartment 1 are drying outundesirably quickly, then he/she can use the selector switch 11 to setan operating state c), for which a timing diagram for the operation ofthe evaporator 5 and fan 9 is illustrated in FIG. 4. While the operatingphases and switched-off phases of the evaporator 5, illustrated by acurve 4 c, alternate in a controlled manner with one another, as in thecurves 4 a and 4 b for operating states a) and b), respectively, independence on the result of the temperature sensor 12, the fan 9 inoperating state c) operates continuously, as is illustrated by thestraight line 9 c. This means that, even when the evaporator 5 has beenswitched off, relatively warm air is taken out of the coolingcompartment 1 into the chamber 8, where it heats the evaporator 5 andcauses ice that has been deposited thereon to thaw. The moisture in theevaporator 5 evaporates rapidly as a result of the forced aircirculation produced by the fan 9, and is, thus, carried out into thecooling compartment 1.

In the case of a further-developed configuration of the refrigeratoraccording to the invention, the cooling compartment 1 contains ahumidity sensor 13 that supplies measured humidity values to the controlcircuit 10. In such a configuration, the selector switch 11 can be usedto set a desired degree of humidity of the cooling compartment 1, thecontrol circuit 10 selecting an operating mode that is suitable forachieving a degree of humidity desired by the user. The control circuit10, here, selects the operating mode a) if the degree of humiditymeasured by the humidity sensor 13 is considerably higher than that setby the selector switch 11, and it selects the operating mode c) if themeasured humidity value is considerably lower than that which has beenset. If the values roughly coincide, use may be made of the operatingmode b).

The operating modes illustrated in FIGS. 2 to 4, of course, onlyconstitute an expedient selection of a large number of possibleoperating modes. It is, thus, possible, for example, in the normaloperating mode, for the fan 9 to be switched on and off in each casewith a certain time delay in relation to the evaporator 5, with theresult that, when the fan 9 is brought into operation, the evaporator 5has already been cooled and, once the evaporator 4 has been switchedoff, the fan 9 continues running for a period of time, in order to makeuse of the residual cold from the former. It is also possible to provideintermediate operating states in each case between the states a) and b)and between b) and c), and so, in one case, the number of shortoperating phases 21 over the duration of the switched-off phase 20 issmaller than is illustrated in FIG. 2 and defrosting of the evaporator 5is not fully ruled out and, in the other case, the operation of the fan9 can be interrupted for a more or less long period of time during aswitched-off phase of the evaporator.

1. A no-frost refrigerator, comprising: at least one storagecompartment; heat insulation; an evaporator disposed separate from saidat least one storage compartment with said heat insulation; and a fanfor driving an exchange of air between said storage compartment and saidevaporator, at least one of said evaporator and said fan being operablewhile the other of said evaporator and said fan is switched off; acontrol circuit connected to said evaporator and said fan forcontrolling operation of said evaporator and said fan, said circuitregulating operation of said evaporator when said fan has been switchedoff to keep a temperature of said evaporator at least one of below atemperature of said storage compartment and below 0° C.; and saidcontrol circuit having an operating-mode selector switch switching oversaid control circuit between at least two operating states selected fromthe group consisting of: a) operation of said evaporator when said fanhas been switched on and, at least temporarily, when said fan has beenswitched off; b) simultaneous operation of said evaporator and said fan;and c) operation of said fan when said evaporator has been switched onand, at least temporarily, when said evaporator has been switched off.2. The no-frost refrigerator according to claim 1, further comprising ahumidity sensor connected to said control circuit for measuring ahumidity value, said humidity sensor switching over said controlcircuit, in dependence on said measured value, between said at least twooperating states.
 3. The no-frost refrigerator according to claim 2,wherein said humidity sensor is disposed on said storage compartment. 4.The no-frost refrigerator according to claim 1, wherein, in saidoperating state a), said control circuit, in each switched-off phase ofsaid fan, keeps said evaporator temporarily switched off and temporarilyswitched on.
 5. The no-frost refrigerator according to claim 1, wherein,in said operating state a), said control circuit, in each switched-offphase of said fan, periodically switches said evaporator on and off. 6.The no-frost refrigerator according to claim 1, wherein, in saidoperating state c), said control circuit operates said fan continuouslyin each switched-off phase of said evaporator.
 7. A no-frostrefrigerator, comprising: at least one storage compartment; heatinsulation; an evaporator disposed separate from said at least onestorage compartment with said heat insulation; a fan for driving anexchange of air between said storage compartment and said evaporator,said fan being operable while said fan is switched off; and a controlcircuit connected to said evaporator and said fan for controllingoperation of said evaporator and said fan, said control circuit forregulating operation of said evaporator when said fan has been switchedoff to keep a temperature of said evaporators at least one of below atemperature of said storage compartment and below 0° C.